This invention relates to portable radiotelephone equipment and more specifically relates to an interface system which enables the automatic incorporation of a remote handset into the operation of the portable radio telephone.
Portable radio transceivers have enabled users to take the capability of radio communication wherever they may go. By the very nature of being portable, the transceivers must be light weight and non-bulky. This nature is generally in opposition to a large storage battery for long duration high powered transmissions and an efficient antenna with unperturbed radiation characteristics. To resolve these problems and to improve transmission and reception performance which usually suffers serious degradation if the portable transceiver is used inside a metal vehicle, transceiver developers have adapted the portable transceiver to be used in a vehicle. The portable transceiver may share the vehicle's battery and utilize the vehicle to support an optimum antenna, thereby increasing both the available duration of transmission and the radio range of the portable transceiver.
Similarly, a portable radiotelephone can benefit from a vehicle's battery and antenna. A radiotelephone, however, has significantly more user interface functions (such as a telephone push button keypad for dialling) than a typical transceiver. When the portable radiotelephone is placed into a converter which mechanically supports the portable and antenna in a vehicle, it is desirable to connect an external telephone handset to the portable radiotelephone. This connection enables user interface elements to be placed advantageously near the user while allowing the portable radiotelephone to be placed out of sight.
Remote handsets have been used with radiotelephones previously. Earlier versions of mobile radiotelephones had the capability of more than one handset; each handset would operate in parallel with the others. Parallel operation, however, did not allow independence of operation. If the external telephone handset and keypad of a portable radiotelephone could be caused to operate independently of the integral handset and keypad, additional capability could be added to the radiotelephone.
Therefore, a portable radiotelephone system which enables a portable radiotelephone to be detachably mounted in a vehicle to share that vehicle's battery and antenna and which additionally enables the portable radiotelephone to utilize a remote handset and keypad which are automatically connected when the portable radiotelephone is placed in the converter would be highly desirable. Furthermore, if the presence or absence of the remote handset could be automatically detected by the portable radiotelephone, additional functions could be made available.